The Primate Embryo Gene Expression Resource permits the rapid and cost-effective study of gene expression in primate oocytes and preimplantation embryos using the rhesus monkey as the primary model organism. PREGER contains over 160 informative samples representing GV-stage oocytes, MII- stage oocytes, and embryos at the 1-cell through hatched blastocyst stages, obtained using different combinations of in vitro or in vivo maturation, fertilization, and culture. This extensive and valuable sample set permits analyses of gene expression related to understanding basic primate embryology, as well as potential effects of clinical procedures on embryo quality using a primate model. Dot blots for expression analysis, cDNA libraries, probes, and other tools in PREGER can be distributed to other scientists, providing unprecedented opportunities for molecular studies in primate embryos. The libraries can be employed for a myriad of other purposes, such as library screening and library subtraction. We propose to maintain the resource, continue to distribute these materials and molecular tools to the scientific community, maintain the PREGER website, extend the resource to encompass samples from baboon in order that the generality of observations among primate species may be evaluated, and incorporate samples of human and rhesus ES lines and rhesus inner cell mass cells for evaluating the developmental potency of human ES lines. We also we propose to apply a novel method for suppression subtraction hybridization that we have developed to be compatible with our amplified libraries, in order to identify novel developmentally regulated genes that are relevant to early primate embryogenesis and that will assist improvements in assisted reproduction methods. This will facilitate basic research, and may support novel clinical approaches, e.g., in the evaluation of embryo quality. The proposed activities will at once maintain and expand the resource, produce new and fundamental basic information about primate embryos, and produce novel molecular approaches that may be useful in clinical practice.